1. Field of the Invention
The present invention relates to an improvement in a tank fitting structure for a fuel pump.
2. Description of Background Art
FIG. 4 of Japanese Pre-examination Patent Publication (KOKAI) No. 8-232792 (1996) xe2x80x9cIn-tank Type Fuel Pump Devicexe2x80x9d shows an in-tank type fuel pump 2 fitted to a fuel tank 1 (the symbols and the numerals used in the No. 8-232792 publication are the same as those used in disclosure of the present invention that follows). A fitting structure consisting of flange 24 of in-tank type fuel pump 2 is shown in detail in FIG. 31 of the publication. FIG. 31 of this publication is reprinted as FIG. 14 herein. The structure shown is described in detail below.
FIGS. 14(a) to 14(c) reprints FIG. 31 of the Japanese Pre-examination Patent Publication (KOKAI) No. 8-232792 (1996), in which 14(c) coincides with FIG. 31, and 14(a) and 14(b) are illustrations of mounting to obtain 14(c).
In FIG. 14(a), presser claw 102 is preliminarily fitted to an edge of pump insertion hole 101 of fuel tank 100, and gasket 103 is positioned on the edge of the pump insertion hole 101. Earth minus terminal 106 is fitted to rib 105 which droops down from flange 104 of the pump. Flange 104 is positioned on the gasket 103 (arrow {circle around (1)}).
FIG. 14(b) shows the condition where flange 104 is positioned on gasket 103, and, while pushing flange 104 as indicated by the downward arrow, stopper metal 107 is lowered to a side of presser claw 102 as indicated by arrow {circle around (2)}. The stopper metal 107 is turned as indicated by arrow {circle around (3)}, whereby stopper metal 107 is hooked under presser claw 102.
FIG. 14(c) shows completion of mounting, in which gasket 103 causes a pushing up force on flange 104. By pressing flange 104 against stopper metal 107, flange 104 is fitted and sealed to fuel tank 100.
The connecting structure created as described above by turning and hooking the stopper metal 107 onto the presser claw 102 on the fixed side is called a snap fit or a bayonet connection. Snap fit and bayonet connections are simple connecting methods and are widely adopted.
However, as is clear from FIG. 14(c), the simple structure leads to dispersion in the collapsing amount of gasket 103. Furthermore, problems exist with snap fit and bayonet connections in the case of, for example, autobicycles which are subject to large vibrations.
One way to address the above issues, may be to consider increasing the size of gasket 103 to increase the collapsing allowance, or to form gasket 103 from a hard material to enhance the spring coefficient. However, with this approach, the pressing force indicated by the downward arrow in FIG. 14(b) would have to be increased, requiring presser claw 102 and stopper metal 107 to be made more rigid, leading to an increase in parts cost. In addition, the turning torque of stopper metal 107 indicated by arrow {circle around (3)} in FIG. 14(b) would have to be increased, making the work of fitting the fuel pump to the tank more difficult.
Further, for lightness in weight and corrosion resistance, flange 104 may sometimes be made of a resin. Resins suffer from deformation called creep when being compressed by a high pressure for a long time. Therefore, increasing the pressing force is not desirable.
Also, when designing a fuel tank for an autobicycle, in many cases the pump unit is inserted into a tank bottom upwards from the lower side, and then fixed to the tank. In such a case, the center of gravity of the pump unit is above the flange, causing a large force to be exerted on the flange at the time of lateral turning. Thus, snap fit or bayonet connections are generally not suitable for such use.
As described above, pump fitting structures according to the prior art are not suitable for vehicles receiving large vibrations such as an autobicycle. Thus, it is the object of the present invention to provide a fitting structure for a fuel pump which replaces the snap fit or bayonet connection.
In order to attain the above object, the present invention includes a gasket that is positioned on an edge of a pump insertion hole provided in a fuel tank. A fixed side ring is preliminarily fitted to the fuel tank at a position for surrounding the gasket, and major part of a pump unit, is inserted into the fuel tank through the pump insertion hole while placing a flange portion projected from the pump unit on the gasket. The inside surface of a presser ring is positioned on the flange portion, and the outside surface of the presser ring faces the fixed side ring. Further, the outside surface of the presser ring is brought into close contact with the fixed side ring by a fastening member, thus fitting the pump unit to the fuel tank.
The gasket is positioned on the flange portion, and the flange portion is pressed by an inside surface of the presser ring thereby collapsing the gasket. The collapsing amount is determined by the position at which the presser ring comes into contact with the fixed side ring. As such, the collapsing amount of the gasket is constant even if the fastening force of the fastening member is increased. When the fastening force of the fastening member is increased, only the connection between the fixed side ring and the presser ring is increased. A compressing force acting on the flange portion coincides with the springy force of the gasket. According to the present invention, the springy force of the gasket is fixed, thus preventing a situation where a compressing force beyond a certain level would be exerted on the flange portion. As such, generation of creep in the flange portion can be obviated, even when the flange portion is made of a resin.
As a result, sealing performance is stabilized, and a good seal can be maintained even under conditions of heavy vibration.
The present invention further includes a fixed side ring formed with first valley portions and first mount portions alternately provided by bending a steel sheet. The first valley portions are connected to the fuel tank, and the first mount portions are used as receiving surfaces for the presser ring. The presser ring is formed with second valley portions and second mount portions alternately provided by bending a steel sheet. These second valley portions are brought into contact with the first mount portions, and the flange portion of the pump unit is held by inside surfaces of the second mount portions.
In order to bring the presser ring into close contact with the fixed side ring and to appropriately press the flange portion by the presser ring, desired shapes are arranged by bending a sheet. Since the rings are formed from a sheet, a reduction in weight of the fixed side ring and the presser ring is possible.
The present invention further includes a flange portion of the pump unit made of a resin. As a result, a reduction of both the weight and the cost of the pump unit is accomplished.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.